The invention relates to liquid crystal light valve projectors, and more particularly to a prism assembly for the illumination of a single light valve with three separate primary color illumination images.
The liquid crystal light valve is frequently employed in high quality large screen projectors. The reflective mode liquid crystal light valve is a thin film multilayer structure comprising a liquid crystal layer, a dielectric mirror, a light blocking layer, and a photoresponsive layer sandwiched between two transparent electrodes. A polarized illumination beam is directed through the liquid crystal layer to the dielectric mirror. An input image of low intensity light, such as that generated by a cathode ray tube, is applied to the photoresponsive layer, thereby switching the electric field across the electrodes from the photoresponsive layer onto the liquid crystal layer to activate the liquid crystal. Linearly polarized illumination light passing through the liquid crystal layer and reflecting from the dielectric mirror is polarization modulated in accordance with the image on the photoresponsive layer. This reflected light is analyzed by a polarizer, which transmits the image bearing component of the reflected light and reflects the other components of the light reflected by the light valve. Therefore, the light valve can be employed to convert a high resolution input image, focused onto the photoresponsive layer, into a replica which can be projected with magnification to produce a high brightness image on a viewing screen.
Insofar as is known to applicant, there are presently no projection systems on the market today using a single liquid crystal light valve with full color capability. All available light valve projector systems known to applicant have required three liquid crystal light valves, one for each of the three primary color images, for full color imagery.
It would therefore be an advance in the art to provide a prism assembly which can be effectively employed with a single light valve to produce full color images.
It would be advantageous to provide a prism assembly for a light valve projection system which contains all the beam splitting elements in one housing, and which both prepolarizes and color separates, and which provides the light valve with three illumination beams.